Technical Field
The present disclosure relates to a nanocomposite film comprising a polymer matrix and conductive nanofiller dispersed in the matrix having a first surface with a first resistivity and a second surface with a second resistivity, a process for producing the nanocomposite film and an electronic device comprising the nanocomposite film.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Polymer composites filled by graphitic nanostructures have attracted significant attention as a result of their unique mechanical, electric and optical properties. Nano-scale conductive fillers can create a seamlessly interconnected percolative network within the polymer matrix altering the energy storing and transporting properties of the composite while reinforcing the native polymer and enhancing its mechanical strength.
Graphene is a two-dimensional arrangement of carbon atoms in a hexagonal lattice with sheets having a thickness of just one atom (0.33 nm). The graphene has a layered crystal structure, in which the carbon atoms are strongly bonded on a two-dimensional network consisting of hexagons. Graphene combines the layered structure of clays with the excellent mechanical, thermal and electrical properties of carbon nanotubes to provide unique functional properties in final products. Since the isolation of a single sheet of graphene [K. S. Novoselov, a K. Geim, S. V Morozov, D. Jiang, Y. Zhang, S. V Dubonos, I. V Grigorieva, a a Firsov, Science (80-.). 306 (2004) 666.—incorporated herein by reference in its entirety], graphene has attracted the attention of researchers pursuing novel nanocomposites [J. Liang, Y. Huang, L. Zhang, Y. Wang, Y. Ma, T. Guo, Y. Chen, Adv. Funct. Mater. 19 (2009) 2297.—incorporated herein by reference in its entirety].
In recent years, graphene has become a preferred nanofiller as a result of its unique characteristics. Graphene is known to be combined as a few layers (graphite) and different types of graphite nanoplatelets such as thermally expanded graphite, graphene oxide (GO) and chemically modified graphene have been used to make functional polymer nanocomposites [H. Kim, A. Abdala, C. W. Macosko, Macromolecules 43 (2010) 6515.; and C. Gómez-Navarro, J. C. Meyer, R. S. Sundaram, A. Chuvilin, S. Kurasch, M. Burghard, K. Kern, U. Kaiser, Nano Lett. 10 (2010) 1144.; and J. T. Robinson, F. K. Perkins, E. S. Snow, Z. Wei, P. E. Sheehan, Nano Lett. 8 (2008) 3137.; and Y. Zhu, S. Murali, W. Cai, X. Li, J. W. Suk, J. R. Potts, R. S. Ruoff, Adv. Mater. 22 (2010) 3906.—each incorporated herein by reference in its entirety]. The initial development of graphene from graphite was via acid treatment (Hummer's reaction) to exfoliate graphene sheets [W. S. Hummers, R. E. Offeman, J. Am. Chem. Soc. 80 (1958) 1339.—incorporated herein by reference in its entirety].
Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer that has been used in numerous applications including water-soluble packaging films, drug delivery, paper coating, textile sizing, etc. PVA is well known for its biocompatibility and non-toxicity and can easily be blended with a wide range of natural polymers and fillers to make biodegradable composites with remarkable properties. Despite many studies, included below, describing several unique nanocomposites, there remain many possibilities for developing different types of graphitic nanocomposites with different morphologies and functionalization for enhancing a number of chemical, mechanical, and electrical properties and for use across industries and disciplines.
For example, Xu et al. [Y. Xu, W. Hong, H. Bai, C. Li, G. Shi, Carbon N. Y. 47 (2009) 3538.—incorporated herein by reference in its entirety] reported the preparation of a PVA/graphene oxide nanocomposite that was shown to be strong and ductile in comparison to the pristine polymer. Liang et al. [J. Liang, Y. Huang, L. Zhang, Y. Wang, Y. Ma, T. Guo, Y. Chen, Adv. Funct. Mater. 19 (2009) 2297.—incorporated herein by reference in its entirety] have also prepared PVA/graphene oxide nanocomposites by a simple solution mixing in water and casting method. The molecular level dispersion of graphene (only 0.7 wt % of graphene oxide) in the polymer matrix significantly improved the mechanical strength properties in comparison to the native polymer.
Furthermore, Cheng et al. [H. K. F. Cheng, N. G. Sahoo, Y. P. Tan, Y. Pan, H. Bao, L. Li, S. H. Chan, J. Zhao, ACS Appl. Mater. Interfaces 4 (2012) 2387.—incorporated herein by reference in its entirety] used PVA/graphene/graphene oxide instead of pristine graphene oxide alone to further improve the properties of PVA nanocomposites. The results showed a 88% increase in tensile strength, a 150% increase in Young's modulus and a 225% increase in elongation at break compared to the native polymer with only a 1% by weight loading of filler. Zhao et al. [X. Zhao, Q. Zhang, D. Chen, P. Lu, Macromolecules 43 (2010) 2357.—incorporated herein by reference in its entirety] prepared a staple dispersion of graphene oxide in water with the aid of sodium dodecyl benzene sulfonate (SDBS) via sonication. The results demonstrated a 150% increase in tensile strength with the addition of 1.8% by weight graphene to the native polymer.
In addition, Huang et al. [H.-D. Huang, P.-G. Ren, J. Chen, W.-Q. Zhang, X. Ji, Z.-M. Li, J. Memb. Sci. 409 (2012) 156.—incorporated herein by reference in its entirety] prepared PVA/graphene oxide nanosheet composites by a simple solution mixing process. A significant change was noted in the barrier property and the results lead to applications in the packaging industry. Wang et al. [C. Wang, Y. Li, G. Ding, X. Xie, M. Jiang, J. Appl. Polym. Sci. 127 (2013) 3026.—incorporated herein by reference in its entirety] reported the characterization and preparation of PVA/graphene oxide nanocomposites via electrospinning methods. The results showed a decrease in decomposition temperature as well as a significant increase (42×) in tensile strength with a very low loading (0.02 wt. % of graphene oxide) in the PVA matrix.
Recently, Ye et al. [Y.-S. Ye, M.-Y. Cheng, X.-L. Xie, J. Rick, Y.-J. Huang, F.-C. Chang, B.-J. Hwang, J. Power Sources 239 (2013) 424.—incorporated herein by reference in its entirety] demonstrated significant improvements in ionic conductivity and methanol crossover for a PVA membrane reinforced with graphene leading to fuel cell applications. Ma et al. [H.-L. Ma, Y. Zhang, Q.-H. Hu, S. He, X. Li, M. Zhai, Z.-Z. Yu, Mater. Lett. 102-103 (2013) 15.—incorporated herein by reference in its entirety] prepared nanocomposite films of PVA and a glucose-reduced graphene oxide (rGO) by a solution blending method. The aqueous suspension stability of rGO was investigated by adding sodium dodecyl benzene sulfonate (SDBS) and poly(N-vinyl-2-pyrrolidone) (PVP). The results showed that PVP enhanced the dispersion of rGO in water significantly better than SDBS. Furthermore, the results showed an increased tensile strength and an increased Young's modulus for the nanocomposite films compared to the native PVA polymer.
In view of the forgoing, one aspect of the present disclosure is to design and provide nanocomposites with a non-uniform and controlled dispersion of conductive nanofillers in a polymeric matrix to introduce electrical conductivity. It is envisioned that by this manner nanocomposites having the same or different local and bulk electrical resistivities can be produced. It will be advantageous to design nanocomposites and processes for economically producing those nanocomposites that efficiently and economically provide a single material having portions and surfaces that function as a conductor, semiconductor or insulator and mixtures thereof in contrast to the bulk material or other portions and surfaces. Furthermore, the present disclosure envisions widespread applications of such materials throughout the disciplines that employ electronic devices.